Angiotensin II (AII) receptors, of which there are two major subtypes, AT1, and AT2, belong to a superfamily of G protein-linked receptors (Gr). Knowledge of the phylogenetic relationships of AII receptors with other member of this family can provide insight into the mechanisms of action and regulatio of these receptors. Substantial progress has been made to elucidate the actions and mechanisms of the AT1 receptors, but those of the AT2 subtypes remain an enigma. Our previous efforts to determine the phylogenetic relationship of AII receptors to other Gr based on partial amino acid sequences, have been ambiguous. To gain an additional perspective on the phylogenetic relationships of AII receptor subtypes and other Gr, this proposa plans to examine nucleic acid sequences. This information may lead to a more definitive phylogenetic characterization of AII receptor subtypes. A second aspect of this project is to determine potential phosphorylation sites on the AII recepto rs of this project is to determine potential phosphorylation sites on the AII receptors that may be involved in receptor desensitization. Amino acids in the intracellular domains of AII receptors will be compared with thos of other Gr that undergo densensitization by phosphorylation.